In the state of the art, it is common to use a global navigation satellite system such the Global Positioning System (GPS) for locating a railway vehicle such a locomotive or a metro. For this purpose, most of the modern railway vehicles comprise a navigation module able to receive and decode navigation signals issued from a satellite system. These navigation signals are usually publically available and provide a navigation solution with some predefined accuracy. Such solution is called “regular” or “low” resolution navigation solution. Generally, this solution is not sufficient for determine precisely the train location and notably, its position on one of the several parallel tracks in a multitrack railway system.
Additionally, in a multitrack system, determination of the precise track of the railway vehicle constitute an important, so called “vital”, application for the railway traffic regulation. Moreover, as the vital applications concern the traffic safety, track information should be known with a high level of certainty.
For such vital applications, it is known to use two redundant navigation modules. However, the accuracy of a navigation solution obtained using the redundant navigation modules is not sufficient. Typically, the accuracy of the railway position determined by the redundant modules is not guaranteed to be better than +/−60 feet (approximately 18.3 meters) while the distance between the adjacent tacks can be less than 12 feet (approximately 3.7 meters).
Consequently, in order to distinguish vitally the tracks one from another, some additional information is required. For example, such information can be based on a track map, on an operator track number entry and/or on using preliminary logic calculations regarding position and direction of travel in conjunction with switch positions until the track is narrowed down to a single track possibility.
It is clear that such additional information is not always available and the necessity of its utilization increases the complexity and the cost of embedded equipment of the railway vehicle. It also increases the exploitation cost of the railway vehicle.